. Bulletins of American paleontology. 99 CiNCINNATIAN CeFHALOPODS : FlOWER 17 VISCERAL MASS There is no direct evidence as to the structure of the visceral mass or the main part of the body of the fossil nautiloids. All of the direct evidence bearing upon this problem is found in what is known of the only living genus of the Nautiloidea, Nautilus itself. As the last survivor of a group of nautiloids which have remained coiled througliout the Mesozoic and Cenozoic, we may suspect that A'autHus may have undergone specializations in tis- sue organization and that the present body pattern may be q
. Bulletins of American paleontology. 99 CiNCINNATIAN CeFHALOPODS : FlOWER 17 VISCERAL MASS There is no direct evidence as to the structure of the visceral mass or the main part of the body of the fossil nautiloids. All of the direct evidence bearing upon this problem is found in what is known of the only living genus of the Nautiloidea, Nautilus itself. As the last survivor of a group of nautiloids which have remained coiled througliout the Mesozoic and Cenozoic, we may suspect that A'autHus may have undergone specializations in tis- sue organization and that the present body pattern may be quite different from that of the orthoceracones which dominated the. H/ 'R 5 'q p Figure 2. Diagrammatic sagittal section of Nautilus showing location of main organs and relation of soft parts to shell. A. Tentacles, surround- ing the mouth. B. Beak. C. Prelingual processes. D. Eadula. E. Tongue. F. First suboesophageal ganglion. G. Oesophagus. H. Supracesophageal ganglion. F and G are a part of a circumoral nerve ring, essentially the brain. I. Crop. J. Portions of the liver. K. Gizzard. L. Space occu- pied by reproductive organs. M. Intestine. N. Heart. O. Nephridia. P. Ctenidia. Q. Portion of cartilage, incompletely represented, forming a capsule in the cephalic region. T?. Shell wall. S. Mantle lobe. T. Dorsal iiiriiitle ]o))o. Ily. Ilypouoine, (ip( iiiiio; of gill ciiaiiilter. TM. Terminal mantle. PM. Posterior mantle. SP. Se].tum. SN. Septal neck. CR. Con- necting ring. CM. Cameral mantle. ST. Siphonal tissue. CS. Cameral space, occupied by liquiil or gas. The tissues of the phragmocone are shown only on the four adoral camerse. SC. Siphonal caecum, termination of siphuncle in apex of Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Paleontological Research Institution (Ithaca, N. Y. ); Columbia
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